Misconceptions and flaws noticed by the more educated...

[Externet]

Hi.
Along the years and the presence of educated professionals in this board; what is found as common electronics misconceptions that may need to be addressed as originated by voids in proper learning of electronics ?
In other words; what do you think should be changed in text books to facilitate understanding and to avoid mistakes - what would you change/improve ?

 

[d123]

Hi,

I don't include myself in your description, but as a layperson I would suggest a section that explains the importance of learning to read datasheets early on and avoid beginner's favourite: that datasheets only have page 1 and a picture of the pinout, and then there's a load of other stuff that doesn't matter after it.

 

[wwfeldman]

i'm certainly over-educated and under experienced, and claim no specific expertise

i agree with d123

and i would add that one needs to develop a greater conceptual understanding and less reliance on simulations

and i would add that one needs to put their backside in a chair and do the work - do every example in the text in great detail
write down, in simple sentences WHY you are doing what you are doing
write down the math, every step
understand the meaning of the equations before you use numbers and units

 

[BradtheRad]

In my experience I keep trying to sort out the terms 'magnetic' and 'electromagnetic'. There is the electromagnetic spectrum covering light/ X-rays/ microwaves/ infrared/ ultraviolet/ radio, etc. These have to do with photons. And these are seen to interact with electricity and magnetism.

Electromagnetism (photons) is not the same as magnetism nor is electromagnetism the same as electricity. Yet some years ago those rays (light/ X-rays/ microwaves/ infrared/ ultraviolet/ radio) got called electromagnetic waves. So what is missing in the textbooks?

 

[wwfeldman]

@BradtheRad

what's missing is the connection
(i expect i'm telling you what you already know)

Before Faraday and Maxwell, electricity was electricity and magnetism was magnetism

permittivity (epsilon) showed up everywhere there was electricity
in free space (vacuum) it was epsilon nought
with a dielectric (as in a capacitor) kappa (the dielectric constant) multiplied epsilon

permeability (mu) showed up everywhere there were magnetic fields
in free space (vacuum) it was mu nought
with a ferromagnetic material (as in a inductors and transformers) (mu) was multiplied by some factor (as appropriate)

Faraday's induction law explained why magnetic fields induced electric fields

around 1850, Maxwell showed that changing E fields induced B fields

so we have Faraday - changing B fields induce E fields
and Maxwell - changing E fields induces B fields
and Maxwell showed that c^2 = 1/(mu nought)(epsilon nought) - the speed of light is related to the two constants
i.e. the electric field constant and the magnetic field constant

recall that in those days, the telegraph was about he best there was and light was the only know electromagnetic wave

There is a reasonable explanation of Maxwell's idea of changing E field inducing magnetic field in Halliday, Resnick and Walker's
physics book but I don't know the chapter number

So we talk about electricity to deal with circuits, including capacitors
we include magnetism to discuss inductors and transformers
and we use electromagnetism to discuss "radio" waves, antennas, and etc

I hope that helped a little

 

[asdf44]

The biggest problems I see is that engineering is so often converted to and taught as math. Doing that makes it easier to teach, easier to grade and lets students 'solve' problems that are beyond their understanding. But it doesn't produce good engineers.

Teach that a transistor is a switch. Then teach that it has a linear region. Then give the equations for those regions (or don't). Not the other way around.
Teach that an opamp is an amplifier. Teach that negative feedback is you driving a car (if too fast then slow down). Then solve opamp circuits. Not the other way around.
Teach signals and systems with mass, springs and dampers which can be more directly understood.

 

[LvW]

When I hear the word "misconception in textbooks" there is one thing which comes immediately in my mind:

1.) I guess that in app. 50% of all textbooks the working principle of bipolar transistor is explained - no sorry: not "explained" - it is just claimed that the BJT would be a current-controlled device.
And the only "proofe" of this wrong statenment is the relation Ic=beta*Ib.

2.) At the same time, all the examples which are presented with the aim to show how a BJT-based amplifier stage is designed is based on a voltage-controlled model.
And - most surprisingly - the authors seem not to realize this contradiction.

(I am aware that this subject was discussed also in this forum already - in some cases with many emotions. It seems that some people who have learned that the BJT would be current-controlled are unable to accept a better - more correct - description. And this - in spite of the fact that there are many proofes for voltage-control)

 

[ThisIsNotSam]

The biggest problems I see is that engineering is so often converted to and taught as math. Doing that makes it easier to teach, easier to grade and lets students 'solve' problems that are beyond their understanding. But it doesn't produce good engineers.

Teach that a transistor is a switch. Then teach that it has a linear region. Then give the equations for those regions (or don't). Not the other way around.
Teach that an opamp is an amplifier. Teach that negative feedback is you driving a car (if too fast then slow down). Then solve opamp circuits. Not the other way around.
Teach signals and systems with mass, springs and dampers which can be more directly understood.

this resonates with me. I remember one circuits class where in order to pass I learned how to use one of those fancy TI calculators to solve LRC systems. I can't remember a single concept from that specific class, no knowledge was acquired.

 

[betwixt]

As a 'layperson' with no formal education or qualifications I would agree with the previous messages. Teach practical first then theory afterwards. Seeing something work then investigating why is far more likely to glue it into someones mind than throwing a million numbers at them and telling them to do something useful with them.

Back in the early 1980's I went to a job interview where they fired a load of questions about DMA at me, thankfully I had used it in a practical situation (a home made Z80 system!) and could answer them. I got the job. Had I not had hands on experience of building the system and only worked from the Z80 family handbooks I doubt I would have managed.

Brian.

 

[KlausST]

Hi,

Theory is urgent, practical experience too.
Whether the one has to be taught before the other... I´m not sure. They should be at least in close proximity. Less than a week.

I had good experience in a school, where we first learned theory then did some practical works.

Theory often is boring, but at least the practical course should be fun. It should make you curious about what happens..

Klaus

 

[Akanimo]

I am always very unhappy when someone tries to teach me and is tell me "'something' is defined as..."

No, don't tell me how something is defined. Tell me what it is.

A lot of textbooks still do this.

 

[d123]

Hi,

Like a lot of what is in this thread.

Agree with wfeldman, it's important to understand that simulations are idealised and are not especially representative of real circuits, not sure if students do or don't understand that.

My personal peeve with how it looks like programmer engineers are taught is that they don't seem to be taught anything whatsoever about the analog parts they will have to use at some point outside of the computer screen. Again, and again: "I've designed an IoT thing that runs the world better than humans with no bugs, but I have a question: What is a resistor?"

No comment besides, how many students and those of us lacking sufficient knowledge to parse our circuits when (God forbid!) you have to troubleshoot a "fail" circuit and experience these points...



Came from here:
View attachment lab8_Log_Antilog_Amplifiers.pdf

Reason for adding it is I think there's a temptation to avoid studying if things work but most learning can come from things not (quite) working or having to contemplate the answers whilst viewing a circuit with the wrong answers and trying to figure out why. Personal experience is e.g. 2 months study = 1 functional (not brilliant) circuit or other that you understand enough but are left with an awareness of still having lagoons in knowledge and understanding.

Personally, hate maths as am very bad at it but I think it's pointless for aspirant engineers not to have the basics clear before any practical work. Maths first, practice, maths after.

I think troubleshooting should come early-ish on perhaps, not as aside towards the end of a book, if at all present. I get the impression "by the end of this book you will never need to troubleshoot ever again or your money back" kind of thing. No doubt I just don't read enough textbooks or that is in fact covered and intended to be understood as a troubleshooting tool early on with Thevenin, Kirschoff et al.

 

[asdf44]

Re: Best topology DCDC adjustable output

To be clear I think theory is important. There is a fine line between education and training and I believe schools should focus on education first.

But I think many fail that. Theory is like a map, if you don't fill in the map from point A to point B teaching how to navigate around point B is worthless.

When you're teaching Ebers–Moll equations before students really understand how to use a transistor as a switch that's what you're doing. That's not theory and that's not education and that's a lot of what my experience has been in the sciences and engineering.

 

[d123]

Hi,

I am always very unhappy when someone tries to teach me and is tell me "'something' is defined as..."

No, don't tell me how something is defined. Tell me what it is.

A lot of textbooks still do this.

What do you mean by that? I just don't understand and would like to.

 

[c_mitra]

Electromagnetism (photons) is not the same as magnetism nor is electromagnetism the same as electricity...

Every charge is associated with an electric field and flow of charge is associated with a magnetic field. Hence every AC circuit is related to electromagnetic principles (what you call electromagnetism or photons).

You are right- light/ X-rays/ microwaves/ infrared/ ultraviolet/ radio- are all electromagnetic waves or photons (as you like it)- and all of them are associated with AC circuits.

You put a charge on a pendulum (oscillating) and the pendulum will radiate electromagnetic waves.

And a photon is nothing but a quantum of the electromagnetic field. That is the basic wave-particle dual nature of all matters.

Modern text books are weak on the basics; the building blocks are not stressed enough.

- - - Updated - - -

No, don't tell me how something is defined. Tell me what it is.

Definitions are the building blocks; if you ignore them you will go into circles.

How can I tell you what is mass, what is charge or what is time? Many people do not have a clear idea about temperature. These are the basic foundations of science and technology.

 

[asdf44]

This isn't exactly education but a common practical mistakes I see new people making is that they trust what they see.

If you measure a node and the multimeter reads 5.2V it means the node you wanted to measure is probably 5.2V but maybe:
-You measured the wrong node
-The multi-meter is in the wrong mode
-The node is oscillating
-The leads are faulty

If you press 'read' in the GUI and it reports 0x4ACD in a register the register is probably 0x4ACD but maybe:
-The register address are wrong
-The value will read something different next time
-Communication isn't established
-The GUI has a bug

I've seen someone read a bad value in a register and spend hours on a debug path when the problem was the GUI wasn't connected. They didn't read any other registers to verify if anything was working.

Bottom line when something doesn't make sense measure it again, and again, measure it differently then move back to anything that's 'solid ground' and take small steps from there.

 

[dick_freebird]

The larger problem may be in expecting textbooks to teach
everything. Especially ones written by professors who have
avoided practical hard-knocks lessons in favor of formulae.

We are awash in textbooks. You could read them all and still
fail at a series of designs. Everybody wants to look at angels
in the architecture but nobody writes a book about how to
pound nails in straight, let alone the folly of trying to pound
screws.

 

[Ratch]

Hi.
Along the years and the presence of educated professionals in this board; what is found as common electronics misconceptions that may need to be addressed as originated by voids in proper learning of electronics ?
In other words; what do you think should be changed in text books to facilitate understanding and to avoid mistakes - what would you change/improve ?

Sure, there are quite a few thing that are taught wrong.

1) Scientific slang such as "current flow", which literally means "charge flow flow", and is redundant and ridiculous. One should instead just say "current", "current exists", or "current is present".

2) Ohm's law wrongly taught as R=E/I. R=E/I is the definition of resistance, not Ohm's law. A resistance follows Ohm's law if its value is constant over a reasonable current range. In other words, if its resistance is linear. This is expounded in physics books written by Halliday & Resnick, and Raymond Serway. A tungsten wire follows Ohm's law. A semiconductor junction does not.

3) Wrongfully claiming that the base current of a BJT controls the collector current. The BE voltage controls the collector current. The base current is the waste current that is somewhat proportional to the collector current, but it is the base leakage effect, not the cause of the of the collector current. The primary cause of the collector current is the BE voltage. A BJT is a transconductance element.

4) Wrongfully averring that batteries and and capacitors "charge" and "discharge". What do they charge up with? The same amount of charge carriers that enter a capacitor or battery leave it for a net gain of zero. What they do charge up is with is energy, so we might as well say they are energized.

5) Wrongfully implying that capacitors carry a current. If you put an ammeter in series with each lead of a capacitor, it will appear to indicate that a current is passing through the capacitor when it is energized. Most textbooks do not emphasize that no charge goes through the dielectric, but instead the charge accumulates on one side of the dielectric and depletes on the other side to give the illusion of current passing through the capacitor.

Silly Science: I will list subjects that I think are out of bounds. Anyone can present a argument why it is feasible. I will give a counter argument.

1) Climate change

2) Evolution

 

[BradtheRad]

Then there's static electricity. A spark is current electricity (lightning bolt, Tesla coil discharge, Ben Franklin's kite-string, etc.), according to books. I guess the books are right. Yet static also creates attractive and repulsive force, similar to magnetism.

I built a spinning bottle motor as described at the links below. It was easy to build. And it worked! Its power came from my tv screen of all things. The screen emanates high-voltage for 30 seconds after power-on.

sci-toys.com/scitoys/scitoys/electro/electro5.html

www.upsbatterycenter.com/blog/make-soda-bottle-motor/

Science books tell about tricks with static charge, such as rubbing a balloon so it sticks to a wall, or rubbing a plastic comb so it picks up confetti. The soda-bottle motor runs on the same operating principle, yet it demonstrates it has an ability to do something practical, perhaps real work. It cannot be called electricity, nor magnetism, nor electromagnetism.

It's static charge which makes the bottle spin. I have not seen a textbook explaining how this force arises, any more than I've seen an explanation how magnetic force arises.

 

[wwfeldman]

@Ratch

"2) Ohm's law wrongly taught as R=E/I. R=E/I is the definition of resistance, not Ohm's law. A resistance follows Ohm's law if its value is constant over a reasonable current range. In other words, if its resistance is linear. This is expounded in physics books written by Halliday & Resnick, and Raymond Serway. A tungsten wire follows Ohm's law. A semiconductor junction does not."

this is an issue of understanding the words

R = E/I is always true.
Ohmic devices - things that have E/I = constant over a large range of E and I, and if you reverse polarity have the same constant, and if E = 0, then I = 0 and visa-versa, like resistors, obey ohms law

non-ohmic devises, such as a semiconductor junction, have a dynamic resistance
R still = E/I, but R changes along the curve
these do not obey ohm's law, but you can still talk about the equivalent resistance at a point along the curve

"Silly Science: I will list subjects that I think are out of bounds. Anyone can present a argument why it is feasible. I will give a counter argument.

1) Climate change

2) Evolution"

does this mean you would argue for climate change and evolution, or against climate change and evolution?
and what do you mean by out of bounds?

@BradtheRad
i have never seen either of those machines
i'll have to build one or both
thanks